As is well-known, motor vehicles include front-mounted headlamps to illuminate vehicle-forward and vehicle-lateral portions of a roadway, improving the driver's ability to see the road and potential hazards or obstacles therein in low-light conditions. A wide variety of headlamp designs are known. At a high level, a vehicle typically includes a pair of front-mounted headlamps disposed substantially at opposed corners of the vehicle front, defining high- and low-beam illumination. This may be done by dedicated high- and low-beam light sources, or by a pair of headlamps each configured to selectively provide a high-beam illumination and a low-beam illumination.
It is desirable for a headlamp to illuminate as much of a vehicle-forward portion of a roadway as possible to maximize the ability of the driver to see. Balanced against this design goal is the need to prevent the vehicle headlamps from emitting light in an orientation that will potentially impair the vision of drivers of vehicles traveling in an opposed direction. For that reason, regulations specify that a beam cutoff, which is an upper border between a headlamp illumination falling above and below a particular intensity, must be located at a certain height above the ground at a specified distance in front of the vehicle.
To comply with such regulations, headlamps are typically made adjustable to allow the manufacturer and subsequently vehicle users to aim the light emitted from the headlamps as needed to provide a desired beam direction. In particular, vertical headlamp aiming is important since, when improperly aimed, a headlamp aimed too low may reduce low light visibility and object detection, or conversely if aimed too high may create glare, discomfort, and potentially hazard to other drivers.
In the manufacturing/assembly context, to analyze/adjust headlamp vertical aim a vehicle under test is placed at a predefined distance from a test surface (colloquially known as a “whiteboard”) and/or measuring device. The headlamps are actuated, and the resulting illumination pattern is analyzed. From the analysis, the headlamps are adjusted to provide the desired illumination direction, beam cutoff, etc. This may occur manually or by use of automated devices, although it is most typical in the manufacturing/assembly context to implement automated/robotic headlamp beam analysis and aiming. Headlamp aiming equipment/systems (“aimers”) are known which use projection analysis or direct measurement of beam cutoff to aim headlamps to nominal position.
Various design and manufacturing factors limit the ability to properly aim a headlamp to nominal position. These factors include manufacturing plant photometric aimer capability. Indeed, the general vertical aiming capability of conventional aimers used in the manufacturing/assembly context is limited to ±3 inches at a distance of 25 feet. This is excessive and does not satisfy customer sensitivity to headlamp vertical aim. Another issue is the short fore-aft distance between the headlamp beam pattern, the vehicle, and the camera systems used to analyse beam patterns, which is conventionally 2-5 feet, compared to the much longer distances at which headlamp aim is audited in the production setting (for example 25 feet in the U.S., and 10 meters in Europe). This magnifies the vertical aim error encountered at the conventional audit distance and beyond.
Specifically, modern headlamps can have a light beam range in the hundreds of feet. All vertical aim errors introduced during headlamp aiming are angular. Therefore, an error introduced at the 5 foot distance conventionally used for current headlamp analysis equipment is magnified at the normal 25 foot audit distance, and even more so at the headlamps range of hundreds of feet. Because of the 1:5-1:10 ratio between production headlamp aiming (2-5 feet) and conventional production headlamp aim auditing (25 feet), any error in vertical aim is magnified by a factor of 5 or more when the audit is performed, which is significant.
Artificial methods have been implemented to compensate for errors introduced by short aiming distances by artificially simulating longer aiming distances, for example Fresnel optical lenses, but are inadequate and indeed may themselves introduce error. A simple solution would be to lengthen the distance between the vehicle and the aiming surface during the production aiming process. However, most production aimers are not and cannot be calibrated for this distance. Moreover, a longer distance between a vehicle and an aiming surface or whiteboard such as 25 feet does not integrate well into current assembly line environment.
To solve this and other problems, the present disclosure relates to systems and methods for vehicle headlamp aiming. Advantageously, the described systems and methods allow a significantly longer aiming distance between a vehicle and an aiming surface, but integrate well into current production/assembly lines. By the ability to use longer aiming distances, vertical and other aiming errors are significantly reduced.